The present invention generally relates to an improved brake system of the type which may be utilized in various mining or drilling operations. One application in which aspects of the present invention may be particularly useful is that of a conveyer utilized to transport bulk materials.
Belt conveyers are often employed in mining operations to transport mined material to a suitable location where it may be discharged for shipping or further processing. As an example, a belt conveyor may be utilized to carry coal or ore from the mine to a nearby rail line. The coal or ore may then be discharged by the conveyor directly into hopper cars of the train. Conveyers of this type are often very lengthy, frequently having a length exceeding a mile or more. Such conveyers are generally driven by a plurality of drive motors spaced apart along their extent.
It should be appreciated that the geographical area in which mining is performed is often relatively hilly. Due to their length, conveyors employed in a hilly area will generally follow the underlying terrain to some degree. Such a conveyer may, therefore, have various segments of different slopes. For example, consider a conveyer having a length of approximately three miles. This conveyer may have a declined segment, a horizontal segment, and an inclined segment, each of which may be one mile or more in length.
The weight of conveyed bulk materials will often impart significant acceleratory forces on declined segments of the conveyer. Unless countered, such forces may tend to cause these segments to run out of control. Horizontal segments may also coast to a degree that is not desired. Accordingly, belt conveyers are usually equipped with suitable brakes to retard acceleration, as well as to regulate stopping time and distance.
Electric drive motors have often been operated in a regenerative mode to provide braking of a belt conveyer. While these motors generally provide effective braking, they often add unnecessary cost to the overall conveyer system. This may be particularly true in a declined segment, where several such motors may be utilized only for purposes of braking.
To reduce overall expenditures, mechanical friction brakes may be utilized in lieu of regenerative motors where appropriate. Such friction brakes may be spring set so that braking torque will be applied in the absence of brake actuation. In this case, electric or hydraulic actuation will cause the braking torque to be selectively lessened.
By their design, friction brakes of this type function to bring a conveyer to a stop in the occurrence of a power failure, as desired. This configuration, however, will generally also cause an interruption in brake cooling after a power failure. In the case of a liquid-cooled brake, for example, such power failure will generally cause the coolant pump to shut down. As a result, a short period of time may transpire in which coolant fluid is not being fed into the brake. During this period, the brake linings may be damaged by the generated heat.
It is also often difficult with mechanical friction brakes to readily ascertain when the brake linings have worn beyond a predetermined threshold.